Welding wire for modified 9Cr-1Mo steel, and submerged-arc welding material

ABSTRACT

A welding wire for a modified 9Cr-1Mo steel is provided which comprises C: 0.070 to 0.150% by mass, Si: more than 0.15% by mass, but not more than 0.30% by mass, Mn: not less than 0.30% by mass, but less than 0.85% by mass, Ni: 0.30 to 1.20% by mass, Cr: 8.00 to 13.00% by mass, Mo: 0.30 to 1.40% by mass, V: 0.03 to 0.40% by mass, Nb: 0.01 to 0.15% by mass, N: 0.016 to 0.055% by mass, P: not more than 0.010% by mass, S: not more than 0.010% by mass, Cu: less than 0.50% by mass, Ti: not more than 0.010% by mass, Al: less than 0.10% by mass, B: less than 0.0010% by mass, W: less than 0.10% by mass, Co: less than 1.00% by mass, and O: not more than 0.03% by mass, wherein the total amount of Mn and Ni being not more than 1.50%. The welding wire provides good toughness without degradation of creep rupture strength even at the PWHT temperature of 760° C. or above.

FIELD OF THE INVENTION

The present invention relates to welding wires for welding modified9Cr-1Mo steels, which are used for various types of heat-resistant andpressure-resistant piping, including a boiler for power generation, aturbine, and the like. More particularly, the invention relates towelding wires for modified 9Cr-1Mo steels, which are used for performinga submerged arc welding (SAW) process of the modified 9Cr-1Mo steel,and/or a tungsten inert gas (TIG) welding process thereof, and towelding materials comprising the combination of the welding wire and aflux.

BACKGROUND OF THE INVENTION

A modified 9Cr-1Mo steel (hereinafter referred to as “Mod.9Cr-1Mosteel”) is made of a 9Cr-1Mo steel with Nb and V added thereto. Forexample, the modified 9Cr-1Mo steel is SA387Gr.91, or SA213Gr.T91, whichis specified in the American Society for Testing and Materials (ASTM)Specification/American Society of Mechanical Engineers (ASME)Specification, X10CrMoVNb9-1, which is specified in the Europeanstandards (EN) Specification, or KA-STBA28, KA-STPA28, KA-SCMV28, orKA-SFVAF28, which is specified in the Technical Standard for ThermalPower Generating Facilities. Hitherto, welding materials, such aswelding wires, for welding these Mod.9Cr-1Mo steels, have been developedvariedly in view of design of the components thereof for improving crackresistance, creep rupture strength, and toughness.

For example, a welding wire has been proposed in Japanese Patent No.2631228 which contains 0.030 to 0.065% by mass of carbon, which isrelatively small, the atomic ratio of Nb and V to C, namely, ((Nb+V)/C),being adjusted within a range of 0.26 to 0.35, so as to have good crackresistance, creep rupture strength, and toughness. Further, in thewelding wire material, Mn is added to the wire for deoxidation and formaintaining strength, and Ni is also added thereto for improvement oftoughness and for decrease of embrittlement in use under hightemperature and pressure conditions for a long time. This documentdiscloses an example in which a post weld heat treatment (PWHT)temperature is 740° C.

JP-A No. 258894/1989 discloses a submerged arc welding method using aflux with a Li compound added thereto so as to have good resistance tointercrystalline crack. This welding method comprises addition of Mn toa welding wire for deoxidation and for maintaining strength, andaddition of Ni to the wire for decrease of embrittlement in use underhigh temperature and pressure conditions for a long time. Further, thispublication discloses an example in which the PWHT temperature is 740°C.

A welding wire disclosed in Japanese Patent No. 2668530 is a weldingwire for a gas-shielded arc welding process. The welding wire contains asmall content of carbon, and optimized contents of Nb and V so as tohave good crack resistance, creep rupture strength, and toughness.Further, in the welding wire, Mn is added to the wire for deoxidationand for maintaining strength, and Ni is also added thereto for decreaseof embrittlement in use under high temperature and pressure conditionsfor a long time. This document discloses an example in which the PWHTtemperature is 740° C.

Japanese Patent No. 2529843 discloses a submerged arc welding methodwhich comprises restricting a Si content of a welding wire to 0.05% bymass or less, while restricting a SiO₂ content of a flux to 5% by massor less so as to have good resistance to intercrystalline crack. Thiswelding method further comprises addition of Mn to the welding wire fordeoxidation and for maintaining strength, and addition of Ni thereto fordecrease of embrittlement in use under high temperature and pressureconditions for a long time. Also, this document discloses an example inwhich the PWHT temperature is 740° C.

In welding wires disclosed in Japanese Patent No. 2594265 and JP-B No.36996/1994, an element W is added to the wire, and a relationshipbetween the W content and the Mo content is optimized, so as to obtaingood creep rupture strength. Further, Mn is added to the welding wirefor deoxidation and for maintaining strength, and Ni is added theretofor decrease of embrittlement in use under high temperature and pressureconditions for a long time. These documents also disclose examples inwhich the PWHT temperature is 750° C.

In welding materials disclosed in Japanese Patent No. 2908228 andJapanese Patent No. 2928904, Ni and Cu are combined and added to thematerials so as to obtain excellent high-temperature strength,high-temperature corrosion resistance, and toughness. Further, Mn isadded to the material so as to fix the S content, thereby preventingharmful effects caused by the element S, including welding cracks, creepembrittlement, and the like, while Ni is added thereto so as to ensuretoughness by improving toughness of a matrix, and restricting theresidual δ-ferrite. Further, these documents also disclose examples inwhich the PWHT temperature is 740° C.

A welding wire disclosed in JP-A No. 96390/1995 contains optimizedcontents of Mn, Ni, and N to obtain good creep rupture strength andtoughness. The Mn is added to the wire for ensuring the strength and forprevention of formation of bulky ferrite, and the Ni is also addedthereto for prevention of formation of the bulky ferrite to stabilizethe toughness. Further, this document also discloses an example in whichthe PWHT temperature is 740° C.

The above-mentioned prior art, however, has the following problems. Insome existing welding methods, approaches are taken in terms of workingconditions to improve the creep rupture strength and toughness. Morespecifically, such an approach involves increasing the PWHT temperature,which is carried out on the overseas working conditions. In statutespertaining to electrical work pieces in Japan (the Technical Standardfor Thermal Power Generating Facilities), the PWHT temperature of highCr ferrite steels, such as the Mod.9Cr-1Mo steel, is set to 760° C. orless. For this reason, on the working conditions in Japan, the PWHTtemperature is intended to be set within a range of 740 to 750° C.,taking into consideration variations in the temperature of a heattreatment furnace, resulting in the actual temperature that does notexceed 760° C. inmost cases. On the other hand, in statutes in othercountries, the PWHT temperature is set to be raised up to an Acltransformation temperature of a base material according to the ASMEspecification, for example. Strictly speaking, there are no rules inother countries that limit the PWHT temperature to 760° C. or less.

Thus, in some welding processes in other countries, the PWHT temperatureis intended to be set to 760° C. for the purpose of improving the creeprupture strength and toughness, and the PWHT temperature is oftenincreased until the actual temperature reaches 780° C. In this case, aproblem of the Acl transformation temperature for a deposited metalarises. Concretely, when the PWHT is carried out at a temperature abovethe Acl transformation temperature of the deposited metal, phasetransformation occurs in the deposited metal, resulting in a danger thatthe creep rupture strength may be significantly degraded. Some recentreports have suggested that, even if the PWHT temperature does notexceed the Acl transformation temperature of the deposited metal, thecreep rupture strength is degraded at the PWHT temperature extremelyclose to the transformation temperature.

From such a background, the American Welding Society (AWS) Specificationand the EN Specification tend to restrict the total content of Mn and Niin the welding material to 1.5% by mass or less for the purpose ofenhancement of the Acl transformation temperature of the depositedmetal. Since there is a negative correlation between the total contentof Mn and Ni and the Acl transformation temperature, decrease in thetotal content of Mn and Ni can raise the Acl transformation temperatureof the deposited metal. Furthermore, as disclosed in the above-mentionedcited documents, since Mn and Ni each have effects of ensuring andimproving toughness, just restriction of the total content of Mn and Niin the welding material under the high PWHT temperature conditiondisadvantageously leads to failure in improvement of the toughness. Theabove-mentioned documents do not take into consideration the weldingmaterial whose PWHT temperature is not less than 760° C. In the weldingmaterials disclosed in these documents, when the PWHT temperatureexceeds the Acl transformation temperature of the deposited metal, phasetransformation might occur in the deposited metal, resulting insignificantly degraded creep rupture strength. Accordingly, a weldingwire for the Mod.9Cr-1Mo steel is required which is usable at the PWHTtemperature of 760° C. or above, and has good toughness.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of those problemsencountered with the prior art, and it is an object of the invention toprovide a welding wire for a modified 9Cr-1Mo steel that provides goodtoughness without degradation of creep rupture strength even at the PWHTtemperature of 760° C. or above.

A welding wire according to one aspect of the invention consistsessentially of, by mass, C: 0.070 to 0.150%, Si: more than 0.15%, butnot more than 0.30%, Mn: not less than 0.30%, but less than 0.85%, Ni:0.30 to 1.20%, Cr: 8.00 to 13.00%, Mo: 0.30 to 1.40%, V: 0.03 to 0.40%,Nb: 0.01 to 0.15%, N: 0.016 to 0.055%, P: not more than 0.010%, S: notmore than 0.010%, Cu: less than 0.50%, Ti: not more than 0.010%, Al:less than 0.10%, B: less than 0.0010%, W: less than 0.10%, Co: less than1.00%, O: not more than 0.03%, and balance: Fe and unavoidableimpurities, the total amount of Mn and Ni being not more than 1.50%.

In the present invention, the total content of Mn and Ni is restrictedto not more than 1.50% by mass, and the Co content is also restricted toless than 1.00% by mass, so that the creep rupture strength is notdegraded even at the PWHT temperature of 760° C. or above. The contentsof Mn, Ni, Si, Cr, Mo, V and Nb, each of which might affect thetoughness, are optimized, while the contents of Al, W, Ti, B, C, and O,each of which might degrade the toughness, are restricted, resulting inthe good toughness.

Preferably, in the welding wire, the Ni content may be 0.40 to 1.00% bymass, the Mo content 0.80 to 1.10% by mass, the Cu content not more than0.10% by mass, and the Al content less than 0.05% by mass. This improvesthe toughness and the creep rupture strength.

A submerged-arc welding material according to another aspect of theinvention consists essentially of, the welding wire with the aforesaidcomponents, and a flux. The flux comprises, by mass, CaF₂: 10 to 60%,CaO: 2 to 25%, MgO: 10 to 50%, Al₂O₃: 2 to 30%, and Si and SiO₂: 6 to30% in terms Of SiO₂.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A welding wire for a modified 9Cr-1Mo steel according to the presentinvention will be hereinafter described in details. The applicant et alhave obtained the following findings from the study of the relationshipbetween wire components and toughness so as to solve the aforesaidproblems. That is, the applicant et al have found that each of Mn and Nicontents should be optimized to have good toughness, and that the besttoughness is achieved by setting the total content of Mn and Ni within arange of 0.60% to 1.50% by mass. Further, the applicant et al have foundthat loadings of the ferrite stabilizing elements should be restrictedso as to prevent the residual δ-ferrite, which might adversely affectthe toughness. For example, when the Mn content, and the Ni content, andthe total content of Mn and Ni are restricted, in particular, thecontents of Si, Cr, Mo, V, Nb, Al, and W among the ferrite stabilizingelements necessarily should be restricted.

Although the element Cu has an effect of preventing the δ-ferrite fromremaining in a weld metal, the excessive amount of added Cu causesembrittlement in the weld metal, resulting in decreased toughness. Also,although the Co has a high effect on improving the toughness bypreventing the δ-ferrite from remaining in the weld metal, the excessiveamount of added Co decreases an Acl transformation temperature and creeprupture strength. The element N has effects of improving the creeprupture strength and of preventing the δ-ferrite from remaining in theweld metal. The excessive amount of N is required to exhibit an effectof improving the toughness by addition of the N to the wire, which mightlead to blowholes. Ti and B are precipitated as fine carbide particlesand fine boride particles, respectively, resulting in significantdegradation of the toughness. Thus, the contents of these elements needto be restricted.

Now, the reason for numeric restriction of a chemical composition of thewelding wire for the modified 9Cr—Mo steel according to the inventionwill be explained below.

C: 0.070 to 0.150% by Mass

The element C has an effect of precipitating various kinds of carbidesin combination with the elements Cr, Mo, W, V, and Nb to improve thecreep rupture strength. Note that in the case of the C content of lessthan 0.070% by mass, this effect is not sufficient. In contrast,excessive addition of the element C, for example, when the C contentexceeds 0.150% by mass, leads to degradation in crack resistance.Accordingly, the C content is preferably 0.070 to 0.150% by mass.

Si: More than 0.15% by Mass, but not More than 0.30% by Mass

The element Si has an effect of acting as a deoxidizing agent todecrease the oxygen amount of a deposited metal, thereby improving thetoughness of the weld metal. Note that the welding wire with the Sicontent of 0.15% by mass or less does not exhibit the effect. Incontrast, since the Si is one of the ferrite stabilizing elements,excessive addition of the Si, for example, when the Si content exceeds0.30% by mass, causes the residual δ-ferrite in the weld metal, thusresulting in degradation of the toughness of the weld metal.Accordingly, the Si content is preferably more than 0.15% by mass, butnot more than 0.30% by mass.

Mn: not Less than 0.30% by Mass, but Less than 0.85% by Mass, Ni: 0.30to 1.20% by Mass, and Mn+Ni: not More than 1.50% by Mass in Total

The element Mn has an effect of acting as a deoxidizing agent todecrease the oxygen amount of the deposited metal, thereby improving thetoughness of the weld metal. Mn and Ni are austenite forming elements,and each of them has an effect of preventing the degradation of thetoughness due to the residual δ-ferrite in the weld metal. Note that inthe case of the Mn content of less than 0.30% by mass, or in the case ofthe Ni content of less than 0.30% by mass, such an effect is notobtained, resulting in the degraded toughness. In contrast, in the caseof the Mn content of at least 0.85%, or in the case of the Ni content ofabove 1.20% by mass, the toughness of the weld metal is degraded. In acase where the total content of Mn and Ni exceeds 1.50% by mass, thetoughness of the weld metal is degraded, while the Acl transformationtemperature of the deposited metal is decreased, thus resulting in thedegraded creep rupture strength. Accordingly, the Mn content ispreferably not less than 0.30% by mass, but less than 0.85% by mass, theNi content 0.30 to 1.20% by mass, and the total content of Mn and Ni notmore than 1.50% by mass. Note that the Ni content is more preferably0.40 to 1.00% by mass. This further improves the toughness of the weldmetal.

Cr: 8.00 to 13.00% by Mass

The element Cr is an important element of the Mod.9Cr-1Mo steel, forwhich the welding wire of the invention is used, and essential forensuring the oxidation resistance and the high-temperature strength. Itshould be noted that when the Cr content is less than 8.00% by mass, theoxidation resistance and the high-temperature strength are insufficient.In contract, since the Cr is one of the ferrite stabilizing elements,excessive addition of the Cr, for example, when the Cr content isgreater than 13.00% by mass, causes the residual δ-ferrite, thusresulting in degradation of the toughness. Accordingly, the Cr contentis preferably 8.00 to 13.00% by mass. This provides the excellentoxidation resistance and high-temperature strength.

Mo: 0.30 to 1.40% by Mass

The element Mo is a solid solution strengthening element, and has aneffect of improving the creep rupture strength. Note that when the Mocontent is less than 0.30% by mass, the sufficient creep rupturestrength is not obtained. In contract, since the Mo is one of theferrite stabilizing elements, excessive addition of the Mo, for example,when the Mo content is greater than 1.40% by mass, causes the residualδ-ferrite in the weld metal, thus resulting in degradation of thetoughness thereof. Accordingly, the Mo content is preferably 0.30 to1.40% by mass, and more preferably 0.80 to 1.10% by mass. This improvesthe creep rupture strength and the toughness.

V: 0.03 to 0.40% by Mass

The element V is a precipitation strengthening element, and has aneffect of precipitating as carbonitride to improve the creep rupturestrength. Note that when the V content is less than 0.03% by mass, thesufficient creep rupture strength is not obtained. In contract, sincethe V is one of the ferrite stabilizing elements, excessive addition ofthe V, for example, when the V content is greater than 0.40% by mass,causes the residual δ-ferrite in the weld metal, thus resulting indegradation of the toughness thereof. Accordingly, the V content ispreferably 0.03 to 0.40% by mass.

Nb: 0.01 to 0.15% by Mass

The element Nb is an element which precipitates as a solid solutionstrengthening nitride to contribute to stabilization of the creeprupture strength. Note that when the Nb content is less than 0.01% bymass, the sufficient creep rupture strength is not obtained. Incontract, since the Nb is one of the ferrite stabilizing elements,excessive addition of the Nb, for example, when the Nb content isgreater than 0.15% by mass, causes the residual δ-ferrite in the weldmetal, thus resulting in degradation of the toughness thereof.Accordingly, the Nb content is preferably 0.01 to 0.15% by mass.

N: 0.016 to 0.055% by Mass

The element N is an element which precipitates as a solid solutionstrengthening nitride to contribute to stabilization of the creeprupture strength. Note that when the N content is less than 0.016% bymass, the sufficient creep rupture strength is not obtained. Incontract, excessive addition of the N, for example, when the N contentis greater than 0.055% by mass, causes blowholes. Accordingly, the Ncontent is preferably 0.016 to 0.055% by mass.

P: not More than 0.010% by Mass

The element P is an element enhancing the sensitivity to hot cracking.When the P content exceeds 0.010% by mass, the hot cracking occurs.Accordingly, the P content is restricted to not more than 0.010% bymass.

S: not More than 0.010% by Mass

The element S is an element enhancing the sensitivity to hot cracking.When the S content exceeds 0.010% by mass, the hot cracking occur.Accordingly, the S content is restricted to not more than 0.010% bymass.

Cu: Less than 0.50% by Mass

The element Cu is an element that degrades the toughness. In some cases,a surface of a wire is coated with Cu plating so as to improveenergizing and feeding properties. As mentioned above, excessiveaddition of the Cu, for example, when the Cu content is not less than0.50% by mass, causes the enbrittlement in the weld metal, resulting indegradation of the toughness. Accordingly, the Cu content in the wholewire including the plating is restricted to less than 0.50% by mass.Note that the Cu content is more preferably restricted to not more than0.10% by mass. This improves the toughness.

Ti: not More than 0.010% by Mass

The element Ti is precipitated as fine carbide to harden the depositedmetal, thus significantly degrading the toughness of the weld metal. Forexample, when the Ti content exceeds 0.010% by mass, the toughness isdegraded. Accordingly, the Ti content is restricted to not more than0.010% by mass.

Al: Less than 0.10% by Mass

The element Al is one of the ferrite stabilizing elements. Excessiveaddition of the Al, for example, when the Al content is not less than0.10% by mass, causes the residual δ-ferrite, which might adverselyaffect the toughness of the weld metal. Accordingly, the Al content isrestricted to less than 0.10% by mass. Note that the Al content ispreferably restricted to less than 0.05% by mass. This improves thetoughness.

B: Less than 0.0010% by Mass

The element B is precipitated as carbon boride and boride to harden thedeposited metal, thus significantly degrading the toughness of the weldmetal. For example, when the B content is not less than 0.0010% by mass,the toughness is degraded. Accordingly, the B content is restricted toless than 0.0010% by mass.

W: Less than 0.10% by Mass

The element W is one of the ferrite stabilizing elements. Excessiveaddition of the W, for example, when the W content is not less than0.10% by mass, causes the residual δ-ferrite in the weld metal,resulting in degradation of the toughness thereof. Accordingly, the Wcontent is restricted to less than 0.10% by mass.

Co: Less than 1.00% by Mass

The element Co is one of the austenite forming elements, and has aneffect of preventing the residual δ-ferrite in the weld metal to improvethe toughness thereof. However, excessive addition of the Co, forexample, when the Co content is not less than 1.00% by mass, decreasesthe Acl transformation temperature of the deposited metal, thusresulting in degradation of the creep rupture strength. Accordingly, theCo content is restricted to less than 1.00% by mass.

O: not More than 0.03% by Mass

The element O remains as the oxide in the deposited metal to degrade thetoughness of the weld metal. For example, when the O content exceeds0.03% by mass, the amount of residual oxide is increased, leading todegradation of the toughness. Accordingly, the O content is restrictedto not more than 0.03% by mass.

In cases where the welding wire of the invention is used for the weldingmethods, such as the submerged arc welding, current polaritysignificantly affects chemical components of the deposited metals,mechanical property, and welding workability. More specifically, directcurrent electrode positive (hereinafter referred to as DCEP) tends toincrease the amount of oxygen in the deposited metal and to degrade thetoughness of the weld metal, as compared to alternating current (AC).Further, the DCEP tends to have magnetic blow-outs, and to cause slugwinding and incomplete fusion. In order to solve such problems, and tohave good mechanical property, the welding wire of the invention ispreferably combined in use with a flux, which comprises CaF₂: 10 to 60%by mass, CaO: 2 to 25% by mass, MgO: 10 to 50% by mass, Al₂O₃: 2 to 30%by mass, and Si and SiO₂: 6 to 30% in terms of SiO₂ by mass in total.

Now, reasons for numeric restriction of a chemical composition of theflux to be used in combination with the welding wire for the modified9Cr—Mo steel of the invention will be explained below.

CaF₂: 10 to 60% by Mass

The compound CaF₂ has an effect of enhancing the basicity of the slug todecrease the amount of oxygen in the deposited metal, thus improving thetoughness of the weld metal. Also, the CaF₂ has an effect of fixing theshape of a weld bead, since CaF2 decreases a melting point of the slugand improves its mobility. Note that when the CaF₂ content in the fluxis less than 10% by mass, such effects are not obtained. When the CaF₂content in the flux exceeds 60% by mass, the mobility of the slug isexcessive, thus significantly impairing the shape of the bead.Accordingly, the CaF₂ content in the flux is preferably 10 to 60% bymass.

CaO: 2 to 25% by Mass

The compound CaO is a basic component, and has an effect of decreasingthe amount of oxygen in the deposited metal to improve the toughness ofthe weld metal, in the same manner as the above-mentioned compound CaF₂.Also, the CaO has an effect of fixing the shape of the weld bead byadjusting the viscosity of the slug. Note that when the CaO content inthe flux is less than 2% by mass, such effects are not obtained. Whenthe CaO content in the flux exceeds 25% by mass, the amount of oxygen inthe deposited metal is increased, leading to degradation of thetoughness of the weld metal. Accordingly, the CaO content in the flux ispreferably 2 to 25% by mass.

MgO: 10 to 50% by Mass

The compound MgO is a basic component, and has an effect of decreasingthe amount of oxygen in the deposited metal to improve the toughness ofthe weld metal, in the same manner as the above-mentioned compound CaF₂.Also, the MgO has an effect of fixing the shape of the weld bead byadjusting the viscosity of the slug. Note that when the MgO content inthe flux is less than 10% by mass, such effects are not obtained. Whenthe MgO content in the flux exceeds 50% by mass, the amount of oxygen inthe deposited metal is increased, leading to degradation of thetoughness of the weld metal. Accordingly, the MgO content in the flux ispreferably 10 to 50% by mass.

Al₂O₃: 2 to 30% by Mass

The compound Al₂O₃ has an effect of enhancing a melting point of theslug to adjust its mobility, thereby fixing the shape of the weld bead.Note that when the Al₂O₃ content in the flux is less than 2% by mass,this effect is not obtained. When the Al₂O₃ content in the flux exceeds30% by mass, slug seizing occurs, and impairs the external appearance ofthe bead. Accordingly, the Al₂O₃ content in the flux is preferably 2 to30% by mass.

Si and SiO₂: 6 to 30% by Mass in Total

The compound SiO₂ has an effect of enhancing the viscosity of the slugto fix the shape of the weld bead. Note that when the SiO₂ content inthe flux is less than 6% by mass, this effect is not obtained. Since theSiO₂ is reduced in an arc to be included in the deposited metal,excessive addition of the SiO₂ increases the amount of reduced Si, whichleads to degradation of the toughness due to the residual δ-ferrite inthe deposited metal. The same goes for the element Si, which isarbitrarily added as a deoxidizing agent into the flux. For this reason,the total amount of Si and SiO₂ in the flux needs to be restricted,including SiO₂ in a soluble glass which is used as a binder whengranulating the flux. Accordingly, the total content of Si and SiO₂ inthe flux is preferably 6 to 30% by mass in terms of SiO₂.

Such essential components can be added in the form of a single material,a compound including these elements themselves, an ore, a fused flux, orthe like. For example, a fluorite may be added as the CaF₂; calcis and amelting flux as the CaO; a magnesia clinker and a melting flux as theMgO; alumina and a melting flux as Al₂O₃; and potassium feldspar,albite, a melting flux, and the like as the SiO₂. In addition to theabove-mentioned essential components, alloy powders, oxides, and/orfluorides may be arbitrarily added to the flux so as to adjust the alloycomponents and the welding workability. Note that unavoidable impuritiesin the welding wire of the invention include Sn, As, Sb, Ca, Mg, and thelike.

EXAMPLE

Now, effects of the examples according to the invention will beexplained by comparing with comparative examples, which depart from thescope of the invention. First, the welding wires with compositions shownin the following Tables 1 and 2 were used as first examples of theinvention. A sample steel plate with a composition shown in Table 3, andhaving a thickness of 20 mm, a groove angle of 45 degrees, and a rootgap of 13 mm, was welded using each of the above-mentioned welding wiresin the submerged arc welding process under a condition shown in thefollowing Table 4. The toughness and creep rupture strength of each ofthe thus-obtained weld metals were evaluated. The following Table 5shows a composition of a combination flux. The combination flux wasobtained by granulating flux raw materials and a water glass as abinder, sintering them at 500 to 550° C. for one hour, so that thecontent of 10×48 mesh grains in the whole flux was 70% by mass or more.Note that the balance shown in the Tables 1 and 2 are Fe and unavoidableimpurities.

-   Table 1-   Table 2-   Table 3-   Table 4-   Table 5

Now, evaluation methods of respective items will be describedhereinafter. First, for classification, radiographic testing (JISspecification Z3104) was performed on the samples after welding. Resultscorresponding to JIS Class 1 were judged as good, and then the sampleswith these results were subjected to the PWHT at 760° C. for two hours.Thereafter, creep rupture and Charpy impact tests were performed onthese samples. The creep test used a specimen with a diameter of 6.0 mmas specified in JIS specification Z2273. And test conditions were asfollows: 650° C., and 86 MPa. The Charpy impact test used a specimen asspecified in JIS specification Z3114, and a test temperature was set to20° C. The respective specimens for the creep rupture and impact testswere extracted from a center part of the weld metal located in thethrough-thickness center region of the obtained plate. Criterions forevaluation of those tests were as follows. In the radiographic testing,the results corresponding to JIS Class 1 were judged good (◯), and theresults other than the JIS Class 1 judged bad (x). In the creep rupturetest, results with a rupture time of not less than 1000 hours werejudged as good (◯), and results with a rupture time of less than 1000hours judged bad (x). In the Charpy impact test, results with vE20° C.average of not less than 40 J were judged good (◯), and results withvE20° C. average of less than 40 J judged bad (x). Those results areshown in the following Tables 7 and 9. The following Tables 6 and 8 showthe chemical components of the deposited metals.

-   Table 6-   Table 7-   Table 8-   Table 9

Now, in second examples of the invention, the welding wires of theexamples No. W43 to W48 and No. W55 to W60 shown in the above Table 2were subjected to wire drawing treatments until a diameter of each wirereached 1.6 mm. A sample steel plate with a composition shown in theabove Table 3, and having a thickness of 12 mm, a groove angle of 45degrees, and a root gap of 6 mm, was welded using each of theabove-mentioned welding wires in the TIG welding process under acondition shown in the following Table 10. The toughness and creeprupture strength of each of the thus-obtained weld metals were evaluatedin the same way and condition as those of the aforesaid first example.Results are shown in the following Table 11.

-   Table 10-   Table 11

As shown in the above Tables 6 and 7, in the wire of the comparativeexample No. W1, the C content was less than that covered by the scope ofthe invention. Thus, the strength of the wire was insufficient, and thecreep rupture time did not satisfy a predetermined requirement ofperformance. In the wire of the comparative example No. W2, the Ccontent exceeded that covered by the scope of the invention, thusleading to occurrence of hot cracking in the radiographic testing. Inthe wire of the comparative example No. W3, since the Si content wasless than that covered by the scope of the invention, the depositedmetal lacked deoxidation, and the toughness of the weld metal did notsatisfy the predetermined requirement of performance. In the wire of thecomparative example No. W4, since the Si content exceeded that coveredby the scope of the invention, the δ-ferrite remained in the weld metal,and the toughness did not satisfy the predetermined requirement ofperformance. In the wire of the comparative example No. W5, since the Mncontent was less than that covered by the scope of the invention, thedeposited metal lacked deoxidation, and the δ-ferrite remained in theweld metal. As a result, the toughness did not satisfy the predeterminedrequirement of performance. In the wire of the comparative example No.W6, the Mn content and the total content of Mn and Ni exceeded thosecovered by the scope of the invention, resulting in the decreased Acltransformation temperature of the deposited metal, and hence the creeprupture time did not satisfy the predetermined requirement ofperformance. Also, the toughness did not meet the predeterminedrequirement of performance.

In the wire of the comparative example No. W7, the P content exceededthat covered by the scope of the invention, thus leading to occurrenceof hot cracking in the radiographic testing. Also, in the wire of thecomparative example No. W8, the S content exceeded that covered by thescope of the invention, thus leading to occurrence of hot cracking inthe radiographic testing. In the wire of the comparative example No. W9,since the Cu content exceeded that covered by the scope of theinvention, the toughness did not meet the predetermined requirement ofperformance. In the wire of the comparative example No. W10, since theNi content was less than that covered by the scope of the invention, theδ-ferrite remained in the weld metal, and the toughness did not satisfythe predetermined requirement of performance. In the wire of thecomparative example No. W11, the Ni content and the total content of Mnand Ni exceeded those covered by the scope of the invention, resultingin the decreased Acl transformation temperature of the deposited metal,and hence the creep rupture time did not satisfy the predeterminedrequirement of performance. Also, the toughness did not meet thepredetermined requirement of performance. In the wire of the comparativeexample No. W12, the Co content exceeded that covered by the scope ofthe invention, resulting in the decreased Acl transformation temperatureof the deposited metal, and hence the creep rupture time did not satisfythe predetermined requirement of performance.

In the wire of the comparative example No. W13, since the Cr content wasless than that covered by the scope of the invention, the strength ofthe wire was insufficient, and the creep rupture time did not satisfythe predetermined requirement of performance. In the wire of thecomparative example No. W14, since the Cr content exceeded that coveredby the scope of the invention, the δ-ferrite remained in the weld metal,and the toughness thereof did not satisfy the predetermined requirementof performance. In the wire of the comparative example No. W15, sincethe Mo content was less than that covered by the scope of the invention,the strength of the wire was insufficient, and the creep rupture timedid not satisfy the predetermined requirement of performance. In thewire of the comparative example No. W16, since the Mo content exceededthat covered by the scope of the invention, the δ-ferrite remained inthe weld metal, and the toughness did not satisfy the predeterminedrequirement of performance. Likewise, in the wire of the comparativeexample No. W17, since the Al content exceeded that covered by the scopeof the invention, the δ-ferrite remained in the weld metal, and thetoughness did not satisfy the predetermined requirement of performance.In the wire of the comparative example No. W18, the Ti content exceededthat covered by the scope of the invention, resulting in significantlyenhancing the strength of the weld metal, and hence the toughness didnot meet the predetermined requirement of performance. In the wire ofthe comparative example No. W19, the Nb content was less than thatcovered by the scope of the invention, leading to insufficient strengthof the wire, resulting in the fact that the creep rupture time did notsatisfy the predetermined requirement of performance. In the wire of thecomparative example No. W20, since the Nb content exceeded that coveredby the scope of the invention, the δ-ferrite remained in the weld metal,and the toughness did not satisfy the predetermined requirement ofperformance.

In the wire of the comparative example No. W21, the V content was lessthan that covered by the scope of the invention, leading to insufficientstrength of the wire, and hence the creep rupture time did not satisfythe predetermined requirement of performance. In the wire of thecomparative example No. W22, since the V content exceeded that coveredby the scope of the invention, the δ-ferrite remained in the weld metal,and the toughness thereof did not satisfy the predetermined requirementof performance. In the wire of the comparative example No. W23, sincethe W content exceeded that covered by the scope of the invention, theδ-ferrite remained in the weld metal, and the toughness thereof did notsatisfy the predetermined requirement of performance. Likewise, in thewire of the comparative example No. W24, the B content exceeded thatcovered by the scope of the invention, resulting in the residualδ-ferrite in the weld metal, and hence the toughness did not meet thepredetermined requirement of performance. In the wire of the comparativeexample No. W25, the N content was less than that covered by the scopeof the invention, leading to insufficient strength. Thus, the creeprupture time failed to satisfy the predetermined requirement ofperformance. In the wire of the comparative example No. W26, the Ncontent exceeded that covered by the scope of the invention, leading tooccurrence of blowholes in the radiographic testing.

In the wire of the comparative example No. W27, the O content exceededthat covered by the scope of the invention, resulting in an increasedoxygen amount in the deposited metal, and thus the toughness did notmeet the predetermined requirement of performance. In the wire of thecomparative example No. W28, the total content of Mn and Ni exceededthose covered by the scope of the invention, resulting in decreased Aclcrystal temperature of the deposited metal, and thus the creep rupturetime did not satisfy the predetermined requirement of performance. Also,the toughness did not meet the predetermined requirement of performance.In the wire of the comparative example No. W29, since the Cu contentexceeded that covered by the scope of the invention, the toughness didnot satisfy the predetermined requirement of performance. Further, sincethe Nb content was less than that covered by the scope of the invention,the strength was insufficient, and hence the creep rupture time did notmeet the predetermined requirement of performance. In the wire of thecomparative example No. W30, the Ni content and the total content of Mnand Ni exceeded those covered by the scope of the invention, resultingin the fact that the toughness did not satisfy the predeterminedrequirement of performance. This decreased the Acl transformationtemperature of the deposited metal. Even addition of the Nb in an amountmore than that covered by the scope of the invention did not allow thecreep rupture time to meet the predetermined requirement of performance.

In contrast, as shown in the above Tables 8 and 9, in the wires of theexamples No. W31 to W60, since the component compositions were withinthe scope of the invention, even when performing the PWHT at 760° C. fortwo hours, the toughness and creep rupture time satisfied thepredetermined requirements of performance. Especially, in the wires No.W49 to W60, the Cu, Ni, Mo, and Al contents each were adjusted within apreferable range, thereby achieving excellent toughness and creeprupture strength. As shown in the above Table 11, the wires No. W43 toW48, and wires No. W55 to W60 satisfied the predetermined requirement ofperformance even in the TIG welding process. In particular, the wiresNo. W55 to W60, in which the Cu, Ni, Mo, and Al contents each werewithin the preferable range, had significantly excellent toughness andcreep rupture strength. TABLE 1 Wire composition (% by mass) No. C Si MnP S Cu Ni Co Cr Mo Al Comparative W1 0.067 0.16 0.65 0.006 0.005 Lessthan 0.02 0.67 Less than 0.02 8.70 0.95 0.005 examples W2 0.158 0.230.55 0.006 0.007 0.03 0.89 Less than 0.02 8.89 0.99 0.010 W3 0.115 0.130.80 0.005 0.002 0.05 0.30 Less than 0.02 9.65 1.05 0.010 W4 0.121 0.330.73 0.005 0.003 0.10 0.45 Less than 0.02 8.23 1.00 0.017 W5 0.126 0.270.24 0.004 0.004 0.03 0.55 0.83 11.50 0.45 0.008 W6 0.137 0.26 0.860.006 0.007 Less than 0.02 1.00 0.54 12.70 0.40 0.009 W7 0.110 0.18 0.740.14 0.008 Less than 0.02 0.60 Less than 0.02 9.50 0.89 Less than 0.002W8 0.080 0.16 0.79 0.005 0.014 Less than 0.02 0.65 Less than 0.02 8.700.75 0.004 W9 0.075 0.17 0.83 0.007 0.005 0.54 0.54 Less than 0.02 8.721.04 0.004 W10 0.074 0.20 0.78 0.005 0.004 Less than 0.02 0.23 0.7811.50 0.53 0.019 W11 0.120 0.24 0.33 0.004 0.005 0.05 1.24 Less than0.02 8.54 0.67 0.030 W12 0.125 0.25 0.43 0.008 0.005 0.20 0.52 1.03 8.450.91 Less than 0.002 W13 0.114 0.26 0.42 0.005 0.006 0.30 0.38 Less than0.02 7.93 0.84 0.050 W14 0.108 0.19 0.55 0.003 0.007 0.04 0.42 Less than0.02 13.11 0.53 0.004 W15 0.120 0.23 0.62 0.005 0.008 0.25 0.55 Lessthan 0.02 8.49 0.21 0.004 W16 0.080 0.25 0.25 0.008 0.005 0.28 0.56 Lessthan 0.02 9.56 1.44 0.010 W17 0.089 0.24 0.38 0.009 0.007 0.40 0.67 Lessthan 0.02 8.95 0.89 0.110 W18 0.093 0.26 0.79 0.008 0.004 Less than 0.020.32 Less than 0.02 8.56 0.94 0.004 W19 0.099 0.16 0.84 0.007 0.003 Lessthan 0.02 0.45 0.89 12.83 0.43 0.005 W20 0.078 0.17 0.70 0.006 0.0030.02 0.52 0.34 9.85 0.85 0.005 W21 0.073 0.19 0.83 0.006 0.003 0.03 0.350.05 8.65 0.86 0.005 W22 0.085 0.16 0.84 0.004 0.005 0.08 0.23 Less than0.02 8.89 0.93 0.070 W23 0.120 0.16 0.75 0.007 0.005 Less than 0.02 0.500.30 8.83 0.92 0.075 W24 0.095 0.23 0.62 0.005 0.005 Less than 0.02 0.45Less than 0.02 8.85 0.99 0.003 W25 0.134 0.17 0.84 0.008 0.008 0.04 0.420.91 10.54 0.37 0.003 W26 0.098 0.16 0.57 0.007 0.007 0.02 0.55 Lessthan 0.02 9.05 0.89 0.003 W27 0.110 0.21 0.65 0.001 0.001 0.05 0.47 Lessthan 0.02 8.93 0.79 0.007 W28 0.095 0.25 0.84 0.007 0.007 Less than 0.020.69 Less than 0.02 8.99 0.95 0.005 W29 0.120 0.24 0.10 0.004 0.004 0.520.55 Less than 0.02 9.65 1.05 0.010 W30 0.108 0.19 0.55 0.002 0.002 0.081.46 Less than 0.02 8.89 0.99 0.010 Wire composition (% by mass) No. TiNb V W B N O Mn + Ni Comparative W1 0.002 0.065 0.280 Less than 0.020.0002 0.040 0.013 1.32 examples W2 0.002 0.047 0.380 Less than 0.020.0003 0.038 0.009 1.44 W3 Less than 0.002 0.052 0.040 0.09 0.0007 0.0500.015 1.10 W4 0.005 0.055 0.240 Less than 0.02 0.0003 0.028 0.005 1.18W5 0.007 0.030 0.230 0.03 0.0003 0.020 0.014 0.79 W6 0.005 0.059 0.350Less than 0.02 0.0003 0.036 0.005 1.86 W7 Less than 0.002 0.130 0.0340.05 0.0003 0.038 0.006 1.34 W8 0.003 0.050 0.190 Less than 0.02 Lessthan 0.0002 0.045 0.008 1.44 W9 0.003 0.048 0.050 Less than 0.02 Lessthan 0.0002 0.051 0.009 1.37 W10 0.004 0.056 0.078 Less than 0.02 Lessthan 0.0002 0.039 0.007 1.01 W11 0.003 0.075 0.190 Less than 0.02 0.00020.033 0.006 1.57 W12 0.005 0.054 0.150 Less than 0.02 0.0002 0.029 0.0060.95 W13 0.007 0.045 0.250 Less than 0.02 0.0003 0.035 0.007 0.80 W14Less than 0.002 0.039 0.240 0.07 0.0003 0.038 0.011 0.97 W15 Less than0.002 0.083 0.240 Less than 0.02 0.0003 0.037 0.010 1.17 W16 0.005 0.0580.190 Less than 0.02 0.0003 0.019 0.008 0.81 W17 0.005 0.059 0.170 Lessthan 0.02 Less than 0.0002 0.026 0.007 1.05 W18 0.012 0.055 0.150 Lessthan 0.02 0.0004 0.032 0.008 1.11 W19 0.004 0.004 0.380 0.03 0.00050.035 0.012 1.29 W20 0.004 0.158 0.037 Less than 0.02 0.0003 0.045 0.0111.22 W21 0.005 0.048 0.022 0.05 0.0003 0.035 0.014 1.18 W22 0.004 0.0560.460 Less than 0.02 0.0003 0.038 0.013 1.07 W23 0.003 0.085 0.200 0.120.0003 0.038 0.011 1.25 W24 0.005 0.062 0.290 Less than 0.02 0.00130.045 0.010 1.07 W25 0.007 0.092 0.050 Less than 0.02 0.0003 0.013 0.0101.26 W26 0.004 0.049 0.190 Less than 0.02 0.0003 0.059 0.012 1.12 W27Less than 0.002 0.048 0.180 Less than 0.02 0.0003 0.036 0.034 1.12 W28Less than 0.002 0.058 0.220 Less than 0.02 Less than 0.0002 0.039 0.0091.53 W29 Less than 0.002 Less than 0.002 0.150 Less than 0.02 0.00050.032 0.008 0.65 W30 0.002 0.163 0.190 Less than 0.02 0.0003 0.033 .00062.01

TABLE 2 Wire composition (% by mass) No. C Si Mn P S Cu Ni Co Cr Mo AlExamples W31 0.085 0.22 0.60 0.002 0.009 0.13 0.35 0.02 11.95 0.71 0.051W32 0.133 0.16 0.46 0.005 0.004 0.32 0.35 0.31 12.71 1.12 0.060 W330.078 0.20 0.74 0.004 0.009 0.35 0.30 0.51 12.29 1.17 0.080 W34 0.1000.20 0.63 0.007 0.003 0.38 0.39 0.58 11.26 1.27 0.072 W35 0.134 0.210.64 0.002 0.002 0.42 0.34 0.36 8.12 1.19 0.098 W36 0.104 0.19 0.480.006 0.008 0.42 0.34 0.04 10.75 1.13 0.098 W37 0.137 0.20 0.37 0.0100.003 0.42 0.39 0.04 11.53 1.17 0.062 W38 0.108 0.16 0.40 0.008 0.0020.46 1.04 0.61 9.04 1.26 0.054 W39 0.091 0.18 0.37 0.002 0.009 0.30 0.360.05 10.21 1.15 0.062 W40 0.108 0.21 0.33 0.007 0.004 0.32 1.03 0.8211.33 0.48 0.087 W41 0.094 0.22 0.40 0.002 0.002 0.36 0.38 0.85 10.771.13 0.053 W42 0.071 0.19 0.32 0.009 0.008 0.39 0.98 0.48 12.39 1.380.093 W43 0.079 0.20 0.73 0.002 0.002 0.41 0.35 0.43 11.12 0.52 0.074W44 0.139 0.18 0.77 0.006 0.002 0.44 0.33 0.62 10.79 0.74 0.084 W450.105 0.18 0.84 0.008 0.002 0.47 0.35 Less than 0.02 12.30 0.62 0.052W46 0.150 0.20 0.76 0.009 0.003 0.49 0.38 0.23 9.02 0.78 0.069 W47 0.0770.21 0.32 0.002 0.003 0.15 1.14 0.72 10.07 0.71 0.078 W48 0.094 0.200.75 0.003 0.004 0.26 0.67 Less than 0.02 8.55 0.93 0.002 W49 0.128 0.230.35 0.010 0.010 Less than 0.02 1.00 0.44 8.94 0.98 0.031 W50 0.141 0.220.75 0.002 0.007 0.07 0.64 0.74 10.39 0.80 Less than 0.002 W51 0.1050.17 0.44 0.005 0.007 0.09 0.84 0.44 11.38 0.85 0.002 W52 0.132 0.210.36 0.004 0.010 0.03 0.74 0.20 9.09 0.80 Less than 0.002 W53 0.118 0.180.36 0.002 0.006 0.06 0.94 0.60 8.18 1.09 0.002 W54 0.133 0.24 0.540.004 0.002 0.03 0.80 0.78 11.18 0.80 0.007 W55 0.121 0.24 0.31 0.0020.002 0.03 0.99 0.82 9.14 0.93 0.005 W56 0.092 0.27 0.32 0.009 0.0020.07 0.77 0.94 8.37 1.01 Less than 0.002 W57 0.115 0.23 0.47 0.002 0.0080.09 0.73 0.39 9.17 0.93 0.005 W58 0.079 0.22 0.37 0.004 0.005 0.06 0.920.24 11.04 1.07 Less than 0.002 W59 0.126 0.16 0.60 0.004 0.006 0.020.79 0.54 10.95 0.69 0.004 W60 0.094 0.30 0.50 0.005 0.004 0.04 0.870.28 12.90 1.10 0.006 Wire composition (% by mass) No. Ti Nb V W B N OMn + Ni Examples W31 0.003 0.063 0.303 0.02 Less than 0.0002 0.018 0.0250.95 W32 0.004 0.047 0.227 0.05 0.0003 0.030 0.026 0.81 W33 0.007 0.1160.379 0.09 0.0003 0.037 0.009 1.04 W34 Less than 0.002 0.091 0.286 Lessthan 0.02 0.0003 0.035 0.005 1.02 W35 0.006 0.036 0.099 0.06 0.00040.038 0.022 0.98 W36 0.007 0.074 0.397 Less than 0.02 0.0003 0.036 0.0290.82 W37 0.007 0.119 0.242 0.08 0.0003 0.016 0.021 0.76 W38 Less than0.002 0.074 0.209 0.09 0.0002 0.051 0.020 1.44 W39 0.009 0.140 0.1480.03 0.0003 0.023 0.010 0.73 W40 0.009 0.038 0.297 0.09 0.0003 0.0550.009 1.36 W41 0.009 0.046 0.057 0.07 Less than 0.0002 0.031 0.023 0.78W42 0.002 0.084 0.287 Less than 0.02 0.0003 0.049 0.027 1.30 W43 0.0060.043 0.265 0.09 0.0003 0.033 0.017 1.08 W44 0.009 0.037 0.125 0.020.0003 0.033 0.015 1.10 W45 0.005 0.067 0.080 0.08 0.0007 0.054 0.0111.19 W46 0.004 0.096 0.235 0.09 0.0005 0.052 0.023 1.14 W47 Less than0.002 0.072 0.080 0.08 0.0003 0.032 0.008 1.46 W48 0.002 0.056 0.220Less than 0.02 0.0009 0.033 0.025 1.42 W49 Less than 0.002 0.094 0.0520.09 0.0003 0.029 0.017 1.35 W50 0.008 0.130 0.182 0.07 0.0003 0.0330.012 1.39 W51 0.002 0.084 0.125 0.02 0.0003 0.053 0.013 1.28 W52 Lessthan 0.002 0.127 0.089 0.04 0.0003 0.028 0.017 1.10 W53 0.002 0.1040.107 0.08 0.0003 0.021 0.012 1.30 W54 0.007 0.028 0.299 0.04 0.00030.031 0.009 1.34 W55 0.005 0.101 0.138 0.03 0.0003 0.054 0.015 1.30 W56Less than 0.002 0.12 0.358 0.06 0.0003 0.017 0.004 1.09 W57 0.005 0.0840.371 0.05 0.0003 0.043 0.020 1.19 W58 Less than 0.002 0.107 0.365 0.060.0003 0.025 0.027 1.29 W59 0.004 0.077 0.081 0.04 0.0003 0.034 0.0221.39 W60 0.006 0.144 0.323 0.04 0.0003 0.047 0.006 1.37

TABLE 3 Type Composition (% by mass) of steel C Si Mn P S Cu Ni Co Cr MoAl Ti Nb V W B N Mod.9Cr—1Mo 0.09 0.32 0.41 0.008 0.007 0.05 0.03 Less8.95 1.02 Less Less 0.08 0.2 Less Less 0.042 Steel than than than thanthan 0.01 0.002 0.002 0.02 0.005

TABLE 4 Welding Power supply Welding Welding Welding Preheating andOther method Wire diameter polarity current voltage Welding speedattitude interpass temperatures condition SAW 2.4 mm DCEP 400 A 29˜30 V30 cm/min Flat 200˜250° C. Single electrode

TABLE 5 Components Content (% by mass) CaF₂ 27 CaO 7 MgO 30 Al₂O₃ 9Total SiO₂ 14 ZrO₂ 3 NaF 2 Fe₂O₃ 1 Mn 0.7 Si 0.5 REM 0.2 Ca 0.2 B₂O₃ 0.1Balance Unavoidable impurities

TABLE 6 Deposited metal composition (% by mass) No. C Si Mn P S Cu Ni CoCr Mo Al Ti Comparative W1 0.052 0.19 0.72 0.008 0.007 Less than 0.020.66 Less than 0.02 8.32 0.94 0.008 0.003 examples W2 0.156 0.29 0.660.008 0.009 0.03 0.90 Less than 0.02 8.45 0.98 0.013 0.003 W3 0.087 0.120.82 0.008 0.004 0.05 0.31 Less than 0.02 8.86 1.02 0.013 Less than0.002 W4 0.117 0.48 0.77 0.008 0.005 0.09 0.45 Less than 0.02 8.02 0.970.020 0.007 W5 0.093 0.43 0.23 0.007 0.006 0.03 0.55 0.82 10.34 0.440.011 0.009 W6 0.126 0.33 1.28 0.008 0.009 Less than 0.02 0.10 0.5511.17 0.39 0.011 0.007 W7 0.095 0.22 0.78 0.015 0.010 Less than 0.020.58 Less than 0.02 8.73 0.86 0.003 0.002 W8 0.046 0.16 0.81 0.008 0.018Less than 0.02 0.65 Less than 0.02 8.09 0.73 0.007 0.005 W9 0.007 0.160.84 0.008 0.007 0.52 0.54 Less than 0.02 8.11 1.03 0.007 0.005 W100.055 0.30 0.81 0.008 0.006 Less than 0.02 0.04 0.78 10.34 0.51 0.0220.006 W11 0.113 0.36 0.36 0.007 0.007 0.04 1.33 Less than 0.02 8.13 0.660.033 0.005 W12 0.093 0.30 0.58 0.008 0.007 0.21 0.52 1.00 8.05 0.890.004 0.007 W13 0.090 0.39 0.57 0.008 0.008 0.28 0.38 Less than 0.027.49 0.82 0.053 0.009 W14 0.086 0.23 0.66 0.005 0.009 0.02 0.42 Lessthan 0.02 11.64 0.52 0.007 0.002 W15 0.120 0.26 0.70 0.008 0.009 0.230.55 Less than 0.02 8.12 0.22 0.007 0.002 W16 0.064 0.31 0.46 0.0080.007 0.27 0.56 Less than 0.02 8.87 1.41 0.013 0.007 W17 0.056 0.31 0.550.011 0.009 0.39 0.70 Less than 0.02 8.31 0.87 0.113 0.007 W18 0.0570.36 0.81 0.008 0.006 Less than 0.02 0.32 Less than 0.02 8.00 0.91 0.0070.014 W19 0.083 0.20 0.88 0.008 0.005 Less than 0.02 0.45 0.88 11.310.40 0.008 0.006 W20 0.079 0.16 0.60 0.007 0.005 Less than 0.02 0.510.30 9.01 0.83 0.008 0.006 W21 0.066 0.16 0.95 0.006 0.005 0.02 0.350.03 8.07 0.85 0.008 0.007 W22 0.059 0.16 1.10 0.007 0.007 0.07 0.25Less than 0.02 8.55 0.91 0.073 0.006 W23 0.093 0.21 0.79 0.008 0.007Less than 0.02 0.49 0.30 8.20 0.91 0.078 0.005 W24 0.078 0.32 0.70 0.0070.007 Less than 0.02 0.44 Less than 0.02 8.23 0.89 0.011 0.007 W25 0.1050.27 0.85 0.009 0.007 0.03 0.42 0.90 9.57 0.35 0.007 0.009 W26 0.0990.24 0.67 0.008 0.009 Less than 0.02 0.55 Less than 0.02 8.36 0.87 0.0060.006 W27 0.076 0.33 0.72 0.004 0.008 0.04 0.49 Less than 0.02 8.26 0.760.009 Less than 0.002 W28 0.064 0.41 0.94 0.008 0.008 Less than 0.020.60 Less than 0.02 8.33 0.93 0.008 0.002 W29 0.112 0.37 0.36 0.0070.007 0.51 0.55 Less than 0.02 8.84 1.03 0.013 0.002 W30 0.078 0.23 0.660.005 0.009 0.07 1.48 Less than 0.02 8.26 0.96 0.014 0.004 Depositedmetal composition (% by mass) No. Nb V W B N O Mn + Ni Comparative W10.042 0.270 Less than 0.02 0.0004 0.035 0.033 1.38 examples W2 0.0300.358 Less than 0.02 0.0005 0.034 0.030 1.56 W3 0.032 0.030 0.04 0.00090.041 0.055 1.13 W4 0.034 0.239 Less than 0.02 0.0005 0.027 0.026 1.22W5 0.019 0.220 0.02 0.0005 0.021 0.052 0.78 W6 0.036 0.340 Less than0.02 0.0005 0.033 0.027 1.38 W7 0.093 0.024 0.03 0.0005 0.035 0.026 1.36W8 0.031 0.180 Less than 0.02 0.0005 0.038 0.028 1.46 W9 0.029 0.040Less than 0.02 0.0003 0.041 0.031 1.38 W10 0.035 0.068 Lese than 0.020.0004 0.036 0.027 0.85 W11 0.049 0.170 Less than 0.02 0.0004 0.0320.026 1.69 W12 0.034 0.130 Less than 0.02 0.0004 0.029 0.026 1.10 W130.028 0.240 Less than 0.02 0.0005 0.034 0.027 0.95 W14 0.024 0.230 0.030.0005 0.035 0.031 1.08 W15 0.054 0.230 Less than 0.02 0.0005 0.0340.030 1.25 W16 0.036 0.170 Less than 0.02 0.0005 0.020 0.028 1.02 W170.037 0.160 Less than 0.02 0.0004 0.027 0.027 1.25 W18 0.034 0.140 Lessthan 0.02 0.0006 0.031 0.028 1.13 W19 0.005 0.360 0.02 0.0007 0.0330.032 1.33 W20 0.120 0.027 Less than 0.02 0.0005 0.040 0.031 1.10 W210.030 0.012 0.03 0.0005 0.033 0.034 1.30 W22 0.035 0.450 Less than 0.020.0005 0.036 0.033 1.35 W23 0.056 0.190 0.06 0.0005 0.035 0.031 1.29 W240.034 0.270 Less than 0.02 0.0015 0.044 0.032 1.14 W25 0.060 0.040 Lessthan 0.02 0.0005 0.014 0.030 1.27 W26 0.032 0.170 Less than 0.02 0.00050.048 0.032 1.22 W27 0.030 0.165 Less than 0.02 0.0005 0.034 0.064 1.21W28 0.038 0.216 Less than 0.02 Less than 0.0002 0.036 0.029 1.54 W29Less than 0.002 0.140 Less than 0.02 0.0005 0.031 0.028 0.91 W30 0.1260.180 Less than 0.02 0.0003 0.032 0.026 2.14

TABLE 7 Radiographic test Creep rupture test Charpy impact test No. WireNo. Results Evaluation Rupture time (Time) Evaluation vE20° C.average(J) Evaluation Comparative 1 W1 JIS Class 1 ◯ 437 X 45 ◯ examples2 W2 Other than JIS Class 1 X — — — — (Hot crack) 3 W3 JIS Class 1 ◯1238 ◯ 15 X 4 W4 JIS Class 1 ◯ 1150 ◯ 19 X 5 W5 JIS Class 1 ◯ 1250 ◯ 13X 6 W6 JIS Class 1 ◯  535 X 15 X 7 W7 Other than JIS Class 1 X — — — —(Hot crack) 8 W8 Other than JIS Class 1 X — — — — (Hot crack) 9 W9 JISClass 1 ◯ 1350 ◯ 25 X 10 W10 JIS Class 1 ◯ 1480 ◯ 11 X 11 W11 JIS Class1 ◯  180 X 19 X 12 W12 JIS Class 1 ◯  459 X 48 ◯ 13 W13 JIS Class 1 ◯ 445 X 54 ◯ 14 W14 JIS Class 1 ◯ 1530 ◯  6 X 15 W15 JIS Class 1 ◯  182 X45 ◯ 16 W16 JIS Class 1 ◯ 1450 ◯  6 X 17 W17 JIS Class 1 ◯ 1350 ◯ 22 X18 W18 JIS Class 1 ◯ 1670 ◯  6 X 19 W19 JIS Class 1 ◯  453 X 75 ◯ 20 W20JIS Class 1 ◯ 1947 ◯ 18 X 21 W21 JIS Class 1 ◯  352 X 36 X 22 W22 JISClass 1 ◯ 1380 ◯ 26 X 23 W23 JIS Class 1 ◯ 1250 ◯ 15 X 24 W24 JIS Class1 ◯ 1870 ◯ 12 X 25 W25 JIS Class 1 ◯  759 X 49 ◯ 26 W26 Other than JISClass 1 X — — — — (Blowhole) 27 W27 JIS Class 1 ◯ 1140 ◯  5 X 28 W28 JISClass 1 ◯  253 X 11 X 29 W29 JIS Class 1 ◯  132 X 20 X 30 W30 JIS Class1 ◯  760 X  5 X

TABLE 8 Deposited metal Composition (% by mass) No. C Si Mn P S Cu Ni CoCr Mo Examples W31 0.067 0.21 0.90 0.006 0.011 0.12 0.34 0.02 10.68 0.69W32 0.118 0.12 0.45 0.007 0.006 0.31 0.23 0.31 11.26 1.10 W33 0.059 0.180.78 0.007 0.011 0.34 0.29 0.51 10.93 1.15 W34 0.083 0.18 0.71 0.0080.005 0.36 0.38 0.58 10.15 1.25 W35 0.118 0.19 0.93 0.006 0.004 0.400.33 0.37 7.73 1.16 W36 0.087 0.17 0.60 0.008 0.010 0.41 0.35 0.04 9.751.11 W37 0.122 0.18 0.47 0.009 0.005 0.41 0.37 0.05 10.35 1.15 W38 0.0910.14 0.55 0.009 0.004 0.45 0.95 0.61 8.44 1.24 W39 0.074 0.15 0.53 0.0060.011 0.30 0.27 0.05 9.34 1.13 W40 0.092 0.19 0.46 0.008 0.006 0.29 0.950.82 10.20 0.46 W41 0.076 0.21 0.55 0.006 0.004 0.35 0.14 0.85 9.77 1.11W42 0.052 0.17 0.49 0.009 0.010 0.37 0.97 0.49 11.01 1.36 W43 0.060 0.180.99 0.006 0.004 0.39 0.25 0.44 10.03 0.50 W44 0.124 0.14 1.02 0.0080.004 0.43 0.29 0.63 9.78 0.72 W45 0.088 0.14 1.17 0.009 0.005 0.46 0.11Less than 0.02 10.94 0.60 W46 0.136 0.18 1.01 0.009 0.005 0.49 0.34 0.238.42 0.76 W47 0.058 0.19 0.35 0.006 0.006 0.14 1.12 0.73 9.23 0.70 W480.076 0.18 0.55 0.005 0.005 0.25 0.31 Less than 0.02 8.21 0.92 W49 0.1130.22 0.44 0.010 0.010 Less than 0.02 0.98 0.44 9.36 0.96 W50 0.126 0.310.79 0.006 0.006 0.06 0.65 0.74 9.48 0.78 W51 0.088 0.25 0.58 0.0070.007 0.08 0.84 0.44 10.23 0.83 W52 0.117 0.30 0.52 0.007 0.007 0.030.74 0.20 8.47 0.78 W53 0.101 0.25 0.52 0.006 0.006 0.05 0.94 0.61 7.781.07 W54 0.117 0.33 0.65 0.007 0.007 0.03 0.81 0.79 10.08 0.78 W55 0.1040.33 0.49 0.006 0.006 0.03 1.00 0.82 8.51 0.91 W56 0.074 0.37 0.48 0.0090.009 0.06 0.77 0.96 7.93 0.98 W57 0.099 0.22 0.60 0.006 0.006 0.08 0.730.39 8.54 0.91 W58 0.060 0.31 0.53 0.007 0.007 0.06 0.92 0.24 9.97 1.05W59 0.110 0.23 0.69 0.007 0.007 0.02 0.79 0.55 9.90 0.67 W60 0.076 0.410.62 0.007 0.007  0.023 0.88 0.28 11.40 1.08 Deposited metal Composition(% by mass) No. Al Ti Nb V W B N O Mn + Ni Examples W31 0.016 0.0040.034 0.290 Less than 0.02 0.0002 0.021 0.038 1.24 W32 0.019 0.005 0.0240.215 0.02 0.0005 0.029 0.037 0.68 W33 0.027 0.008 0.070 0.366 0.040.0004 0.034 0.030 1.07 W34 0.023 0.002 0.053 0.274 Less than 0.020.0004 0.032 0.026 1.09 W35 0.033 0.008 0.016 0.088 0.03 0.0006 0.0340.039 1.26 W36 0.031 0.009 0.042 0.383 Less than 0.02 0.0005 0.033 0.0350.95 W37 0.021 0.009 0.072 0.230 0.04 0.0005 0.019 0.039 0.84 W38 0.018Less than 0.002 0.042 0.197 0.04 0.0004 0.044 0.038 1.50 W39 0.020 0.0110.087 0.137 Less than 0.02 0.0005 0.024 0.030 0.80 W40 0.029 0.011 0.0170.284 0.04 0.0005 0.046 0.029 1.41 W41 0.017 0.011 0.023 0.046 0.040.0002 0.029 0.039 0.69 W42 0.031 0.004 0.048 0.274 Less than 0.020.0005 0.042 0.037 1.46 W43 0.025 0.008 0.021 0.253 0.04 0.0005 0.0310.036 1.24 W44 0.027 0.011 0.017 0.114 Less than 0.02 0.0005 0.031 0.0341.31 W45 0.017 0.007 0.037 0.070 0.04 0.0009 0.046 0.031 1.28 W46 0.0230.006 0.057 0.224 0.04 0.0006 0.044 0.039 1.35 W47 0.024 Less than 0.0020.040 0.069 0.04 0.0005 0.030 0.028 1.47 W48 0.003 0.003 0.038 0.200Less than 0.02 0.0010 0.031 0.038 0.86 W49 0.010 Less than 0.002 0.0550.042 0.05 0.0004 0.028 0.036 1.42 W50 0.002 0.010 0.080 0.171 0.050.0004 0.031 0.032 1.44 W51 0.007 0.004 0.048 0.114 Less than 0.020.0004 0.045 0.033 1.42 W52 0.016 Less than 0.002 0.078 0.078 0.020.0004 0.027 0.036 1.26 W53 0.015 0.004 0.062 0.096 0.04 0.0004 0.0220.032 1.46 W54 0.012 0.009 0.010 0.287 0.02 0.0004 0.030 0.029 1.45 W550.016 0.007 0.060 0.127 0.02 0.0005 0.046 0.034 1.48 W56 0.012 Lessthen0.002 0.074 0.345 0.03 0.0004 0.019 0.025 1.25 W57 0.002 0.007 0.0490.358 0.02 0.0004 0.038 0.038 1.33 W58 0.006 Less than 0.002 0.064 0.3520.03 0.0004 0.025 0.037 1.45 W59 0.003 0.006 0.044 0.070 0.02 0.00050.031 0.038 1.48 W60 0.007 0.008 0.089 0.311 0.02 0.0004 0.041 0.0271.49

TABLE 9 Radiographic test Creep rupture test Charpy impact test No. WireNo. Results Evaluation Rupture time (Time) Evaluation vE20° C.average(J) Evaluation Examples 31 W31 JIS Class 1 ◯ 1370 ◯ 68 ◯ 32 W32JIS Class 1 ◯ 1154 ◯ 75 ◯ 33 W33 JIS Class 1 ◯ 1668 ◯ 71 ◯ 34 W34 JISClass 1 ◯ 1902 ◯ 78 ◯ 35 W35 JIS Class 1 ◯ 1987 ◯ 86 ◯ 36 W36 JIS Class1 ◯ 1144 ◯ 76 ◯ 37 W37 JIS Class 1 ◯ 1144 ◯ 75 ◯ 38 W38 JIS Class 1 ◯1896 ◯ 95 ◯ 39 W39 JIS Class 1 ◯ 1730 ◯ 76 ◯ 40 W40 JIS Class 1 ◯ 1954 ◯47 ◯ 41 W41 JIS Class 1 ◯ 1885 ◯ 79 ◯ 42 W42 JIS Class 1 ◯ 1930 ◯ 85 ◯43 W43 JIS Class 1 ◯ 1750 ◯ 57 ◯ 44 W44 JIS Class 1 ◯ 1902 ◯ 66 ◯ 45 W45JIS Class 1 ◯ 1911 ◯ 65 ◯ 46 W46 JIS Class 1 ◯ 1839 ◯ 78 ◯ 47 W47 JISClass 1 ◯ 1955 ◯ 60 ◯ 48 W48 JIS Class 1 ◯ 1402 ◯ 88 ◯ 49 W49 JIS Class1 ◯ 3450 ⊚ 123 ⊚ 50 W50 JIS Class 1 ◯ 2579 ⊚ 118 ⊚ 51 W51 JIS Class 1 ◯2702 ⊚ 116 ⊚ 52 W52 JIS Class 1 ◯ 2319 ⊚ 110 ⊚ 53 W53 JIS Class 1 ◯ 3692⊚ 124 ⊚ 54 W54 JIS Class 1 ◯ 2191 ⊚ 107 ⊚ 55 W55 JIS Class 1 ◯ 2591 ⊚117 ⊚ 56 W56 JIS Class 1 ◯ 2598 ⊚ 114 ⊚ 57 W57 JIS Class 1 ◯ 2679 ⊚ 128⊚ 58 W58 JIS Class 1 ◯ 2338 ⊚ 126 ⊚ 59 W59 JIS Class 1 ◯ 3152 ⊚ 118 ⊚ 60W60 JIS Class 1 ◯ 2023 ⊚ 115 ⊚

TABLE 10 Preheating and Welding Power supply Welding Welding Weldinginterpass method Wire diameter polarity current voltage Welding speedattitude temperatures Shielding gas TIG 1.6 mm DCEP 240 A 10˜13 V 10cm/min Flat 200˜250° C. Composition: 100% Ar Flow rate Inside 25 L/minOutside 25 L/min

TABLE 11 Radiographic test Creep rupture test Charpy impact test No.Wire No. Results Evaluation Rupture time (Time) Evaluation vE20° C.average(J) Evaluation Examples 61 W43 JIS Class 1 ◯ 1545 ◯ 91 ◯ 62 W44JIS Class 1 ◯ 1779 ◯ 109 ◯ 63 W45 JIS Class 1 ◯ 1460 ◯ 126 ◯ 64 W46 JISClass 1 ◯ 1391 ◯ 110 ◯ 65 W47 JIS Class 1 ◯ 1769 ◯ 125 ◯ 66 W48 JISClass 1 ◯ 1283 ◯ 111 ◯ 67 W55 JIS Class 1 ◯ 3502 ⊚ 148 ⊚ 68 W56 JISClass 1 ◯ 3871 ⊚ 149 ⊚ 69 W57 JIS Class 1 ◯ 3550 ⊚ 176 ⊚ 70 W58 JISClass 1 ◯ 3354 ⊚ 168 ⊚ 71 W59 JIS Class 1 ◯ 4109 ⊚ 164 ⊚ 72 W60 JISClass 1 ◯ 2163 ⊚ 155 ⊚

1. A welding wire consisting essentially of, by mass, C: 0.070 to0.150%, Si: more than 0.15%, but not more than 0.30%, Mn: not less than0.30%, but less than 0.85%, Ni: 0.30 to 1.20%, Cr: 8.00 to 13.00%, Mo:0.30 to 1.40%, V: 0.03 to 0.40%, Nb: 0.01 to 0.15%, N: 0.016 to 0.055%,P: not more than 0.010%, S: not more than 0.010%, Cu: less than 0.50%,Ti: not more than 0.010%, Al: less than 0.10%, B: less than 0.0010%, W:less than 0.10%, Co: less than 1.00%, O: not more than 0.03%, andbalance: Fe and unavoidable impurities, the total amount of Mn and Nibeing not more than 1.50%.
 2. The welding wire according to claim 1,wherein the Ni content is 0.40 to 1.00% by mass.
 3. The welding wireaccording to claim 1, wherein the Mo content is 0.80 to 1.10% by mass.4. The welding wire according to claim 1, wherein the Cu content is notmore than 0.10% by mass.
 5. The welding wire according to claim 1,wherein the Al content is less than 0.05% by mass.
 6. A submerged-arcwelding material, consisting essentially of, the welding wire accordingto claim 1, and a flux, said flux comprising, by mass, CaF₂: 10 to 60%,CaO: 2 to 25%, MgO: 10 to 50%, Al₂O₃: 2 to 30%, and Si and SiO₂: 6 to30% in terms of SiO₂.
 7. The welding material according to claim 6,wherein the Ni content of the welding wire is 0.40 to 1.00% by mass. 8.The welding material according to claim 6, wherein the Mo content is0.80 to 1.10% by mass.
 9. The welding material according to claim 6,wherein the Cu content is not more than 0.10% by mass.
 10. The weldingmaterial according to claim 6, wherein the Al content is less than 0.05%by mass.